Amateur astronomers from Shoalhaven Australia

Cygnus

The constellation of Cygnus, the Swan is located up from the northern horizon to an altitude of about 27° in the Shoalhaven (Southern hemisphere).

It hardly needs to be stated that the viewing of many parts of Cygnus will require little or no geographical obstruction to the north together with minimal atmospheric disturbance.

Cygnus represents a swan flying down the Milky Way. In Greek mythology, the swan was the guise in which the god Zeus visited Leda, wife of the King of Sparta; the result of their union was Castor and Pollux, the heavenly twins. The flying swan’s tail is marked by the star Deneb, its beak by Albireo, and its wings by δ and ε Cyg. These four stars form a distinctive cross shape, referred to as the Northern Cross. Cygnus lies in a rich part of the Milky Way, which is split here by a dark lane of dust known as the Cygnus Rift or the Northern Coal sack. Deneb forms one corner of the Summer Triangle, completed by Altair, αAql, and Vega, αLyr.

This constellation can be found by locating the bright primary star in Lyra, Vega, αLyr, which, at this time and date, lies just west of NNW and 13° altitude. Looking to the right of this star, at four degrees less altitude, and in a direction just slightly west of north, a star of similar brightness to Vega will be seen. This star is Deneb, αCyg, the primary star of this constellation.

Features of Interest:

αCyg, named Deneb, the ‘tail’, at magnitude 1.2, is a blue-white supergiant lying about 3200ly away.

βCyg, named Albireo, 380ly away, is one of the sky’s showpiece doubles. It consists of contrasting amber and blue-green stars, like a celestial traffic light. The brighter one, of magnitude 3.1, is an orange giant, and its blue-green companion is magnitude 5.1, separation 34”, PA 054°. They can be separated through good binoculars and are a beautiful sight in most telescopes.

γCyg, named Sadr, the ‘breast’, is a yellow-white supergiant of magnitude 2.2 and is 1500ly distant.

δCyg, 170ly away, is a magnitude 2.9 blue-white giant with a close, magnitude 6.6, companion, separation 2.4”, PA 225°. These stars have an orbital period of over 800 yrs. High telescopic magnification is required to separate the pair.

εCyg, named Gienah, the ‘wing’, at magnitude 2.5, is an orange giant, 72ly distant.

μCyg, is a pair of white stars of magnitudes 4.8 and 6.2, separation 1.6”, PA 300°, orbiting each other about every 790 yrs. They are currently closing slowly and should remain divisible until about 2020. For our younger members, they will be at their closest in the period 2043 to 2050!

χCyg, 350ly distant, is a red giant long-period variable of the Mira type that varies every 400 days or so. At its brightest, it reaches magnitude 3.3, fading to 14th magnitude at its faintest. Mira itself is the only variable of this type that exceeds this star, which has a diameter of about 300 Suns.

30,31Cyg, are thought to form perhaps the most beautiful binocular double in the heavens. The stars are orange and turquoise, magnitudes 3.8 and 4.8, 1400ly and 720ly, respectively. Separation is 5’37”. The larger star has a closer blue 7.0 magnitude companion.

M39, (NGC 7092), is a loose cluster of about 30 stars of 7th magnitude and fainter, arranged in a triangle. It is 950ly away, and is visible in binoculars given a clear northern sky.

NGC 6992, is the brightest part of the Veil Nebula, the remnant of a supernova explosion 30,00 years ago. Under ideal conditions, this nebula can be seen in binoculars as a faint arc. This is an ideal astro-photographic subject. It lies 2000ly away.